Mysql float double Type

1. float Type
The float column type cannot be found by default. The precision must be specified,
For example, numFloat,InsertTable (num) values (0.12); select* From table where num = 0.12, empty set.
Num float (9, 7 ),InsertTable (num) values (0.12); select* If from table where num = 0.12, this record is found.

Mysql> create table tt
-> (
-> NumFloat (9, 3)
-> );
Query OK, 0 rows affected (0.03 sec)

Mysql> insert into tt (num) values (1234567.8 );
ERROR 1264 (22003): Out of range value for column 'num' at row 1
Note: The field is out of the range and cannot be inserted.

Mysql> insert into tt (num) values (123456.8 );
Query OK, 1 row affected (0.00 sec)

Mysql> select* FromTt;
+ ------------ +
| Num|
+ ------------ +
| 1, 123456.797 |
+ ------------ +
1 row in set (0.00 sec)
Note: If the number of decimal places is not enough, it is automatically filled. However, there is a problem that the approximate values above exist.

Mysql> insert into tt (num) values (123456.867 );
Query OK, 1 row affected (0.04 sec)

Mysql> select * fromTt;
+ ------------ +
| Num|
+ ------------ +
| 1, 123456.797 |
| 1, 123456.797 |
| 1, 123456.867 |
+ ------------ +
3 rows in set (0.00 sec)

Mysql> select* From tt whereNum = 123456.867;
+ ------------ +
| Num|
+ ------------ +
| 1, 123456.867 |
+ ------------ +
1 row in set (0.00 sec)

Mysql> insert into tt (num) values (2.8 );
Query OK, 1 row affected (0.04 sec)

Mysql> select * fromTt;
+ ------------ +
| Num|
+ ------------ +
| 1, 123456.797 |
| 1, 123456.797 |
| 1, 123456.867 |
|2.800 |
+ ------------ +
4 rows in set (0.00 sec)

Mysql> select* From tt whereNum = 2.8;
+ ------- +
| Num|
+ ------- +
| 1, 2.800 |
+ ------- +
1 row in set (0.00 sec)

Mysql> insert into tt (num) values (2.888888 );
Query OK, 1 row affected (0.00 sec)

Mysql> select* FromTt;
+ ------------ +
| Num|
+ ------------ +
| 1, 123456.797 |
| 1, 123456.797 |
| 1, 123456.867 |
|2.800 |
|2.889 |
+ ------------ +
5 rows in set (0.00 sec)
Note: If the number of decimal places exceeds the upper limit, the approximate value is automatically obtained.

Bytes --------------------------------------------------------------------------------------

2. double Type

Mysql> create table tt (
-> NumDouble (9, 3)
-> );
Query OK, 0 rows affected (0.02 sec)

Mysql> insert into tt (num) values (234563.9 );
Query OK, 1 row affected (0.00 sec)

Mysql> select * fromTt;
+ ------------ +
| Num|
+ ------------ +
| 1, 234563.900 |
+ ------------ +
1 row in set (0.00 sec)

Mysql> insert into tt (num) values (2345623.2 );
ERROR 1264 (22003): Out of range value for column 'num' at row 1
Mysql> insert into tt (num) values (234563.2 );
Query OK, 1 row affected (0.00 sec)

Mysql> select* FromTt;
+ ------------ +
| Num|
+ ------------ +
| 1, 234563.900 |
| 1, 234563.200 |
+ ------------ +
2 rows in set (0.00 sec)

Mysql> insert into tt (num) values (2.8 );
Query OK, 1 row affected (0.00 sec)

Mysql> select* From tt;
+ ------------ +
| Num|
+ ------------ +
| 1, 234563.900 |
| 1, 234563.200 |
|2.800 |
+ ------------ +
3 rows in set (0.00 sec)

FLOAT (M, D), REAL (M, D), or double precision (M, D ). Here, "(M, D)" indicates that the value displays a total of M-bit integers, where D is behind the decimal point.
For example, a column defined as FLOAT (999.9999) can be displayed. MySQL returns a rounded value when saving the value. Therefore, if 999.00009 is inserted in the FLOAT (999.0001) column, the approximate result is.